Vibrator



June 13, 1961 G. L. MALAN 2,988,337

VIBRATOR Filed Dec. 22, 1958 3 Sheets-Sheet 1 57 F' 6. 2. r l 6/ 55 INVENTOR. 60 GEORGE L. MALAN BY A T T'ORNE Y8 June 13, 1961 MALAN 2,988,337

VIBRATOR Filed Dec. 22, 1958 3 Sheets-Sheet 2 INVENTOR. GEORGE L NALAN G. L. MALAN June 13, 1961 VIBRATOR 3 Sheets-Sheet 3 Filed Dec. 22, 1958 INVENTOR. R65 L .MA LAN GEO A TTORIVE Y3 United States Patent 2,988,337 VIBRATOR George L. Malan, 821 Viceroy Ave., Covina, Calif. Filed Dec. 22, 1958, Ser. No. 782,096 8 Claims. (Cl. 259-1) This invention relates to an eccentric vibrator of the type useful for distributing and compacting viscous substances such as wet concrete, and the like.

The need for packing and distributing wet concrete throughout the entire volume of a form is well known, and many devices have been proposed for the purpose. One well-known type is shown in Malan Patents 2,187,- 088 and 2,743,090, issued January 16, 1940 and April 24, 1956, respectively. This type of vibrator is simple and involves few moving parts, principally a rotor which rolls around inside a larger race thereby exerting an eccentric force.

The rotor in this type of vibrator is caused to roll by creating compartments for receiving air under pressure at the peripheral surface of the rotor. Each compartment is formed between a vane which is forced outwardly from the rotor to contact the race, and the race and rotor. As pressurized fluid such as compressed air is admitted to each compartment in sequence, the compartment is expanded, thereby rolling the rotor around the race. When the compartment reaches maximum volume, it is connected to exhaust means. Further rolling of the rotor exhausts the air, and the cycle is thereafter begun again. This action is carried out in sequence, a plurality of compartments being spaced around the rotor, so the result is a continuous rolling of the rotor.

The vibrators shown in the aforesaid two patents have stood up well and have given good service. However, it has been found that they are relatively inefiicient consumers of compressed air. In addition, their vanes have sometimes worn down more rapidly than desired, requiring disassembly and repair which ought to be minimized. Excessive down time of such vibrators results either in the need to store extra units for use in the event of breakdown, or of tolerating work stoppage on a pouring job, both of which are expensive.

Accordingly, it is an object of this invention to provide improvements for a vibrator of the type described, by

means of which the efiiciency and longevity of the devices are increased.

A preferred but optional feature of this invention resides in maintaining a continuous fluid pressure in passageways supplying air to the compartments at a point immediately adjacent the compartments, and providing valve means actuable by contact with the race for governing the flow of air to the respective compartments. This is a considerable improvement over prior arrangements, wherein the valving was performed at the end of the rotor, according to which arrangements it was necessary for pressure to change throughout a relatively voluminous passageway system before there was any significant pressure efiect in the compartment itself. The instant arrangement, in ef fect, reduces the volume whose pressure must be changed in order to actuate the device.

Another preferred but optional feature of the invention resides in providing retraction means for the vanes used in the device. As shown in detail in Malan Patent No. 2,743,090, it is advantageous to use vanes whose total throw is insufiicient to maintain the vane in constant contact with the race. This advantage has been offset by the hard usage the vane receives when it strikes the race. This feature reduces the wear on the vanes.

Still another preferred but optional feature resides in means for pillowing the outward movement of the vanes ency to break.

ice

The above and other features of this invention will be fully understood from the following detailed description, and the accompanying drawings, in which:

FIG. 1 is a side elevation, partly in cutaway crosssection, showing the vibrator of this invention;

FIG. 2 is a fragmentary view, in cross-section, showing valving means according to this invention;

FIG. 3 is a cross-section, looking upwardly, taken at line 33 of FIG. 1, showing the rotor at one operative position;

FIG. 4 is a cross section similar to FIG. 3, showing the rotor at another operative position;

FIG. 5 is a cross-section of an end plate for use with the rotor shown in FIG. 7;

FIG. 6 is a fragmentary cross-section of an optional type of slot for use in accordance with this invention;

FIG. 7 is a plan view, partly in cross-section, showing another form of rotor for use in this invention;

FIGS. 8 and 9 are plan views, partly in cutaway crosssection, showing a vibrator-including the end plate of FIG. 5 and the rotor of FIG. 7' in two different operative positions; and

FIG. 10 is a fragmentary cross-section taken at line 10- 10 of FIG. 6.

As best shown in FIG. 1, the vibrator 10 is connected to a pair of concentric hoses: a first central pressure hose l1, and a surrounding exhaust hose 12. The central pressure hose is attached to an inlet pipe 13 and the exhaust hose is attached to the neck 14 of an end member 15. The inlet pipe 13 is threaded through a central hole 16 in the end member 15.

An annular chamber 17 surrounds the pipe 13 and makes fluid communication through passage 18 with an exhaust ring 19 which is a groove formed in the inner face 20 of the end member 15. The face 20 is smooth and planar, being interrupted only by the exhaust ring 19 and the opening at the hole 16. The opening of inlet pipe 13 provides a stationary pressure inlet port 21, which is located on the central axis 22 of the device. The exhaust ring 19 provides a stationary exhaust port which is concentric with the port 21 around the central axis.

A cylinder 23 having an internal cylindrical race 24 has one of its ends fixed by welding or other means to the end member 15, and has attached to its other end a second end member 25. These attachments are air-tight. End member 25 is provided with a centrally disposed stationary inlet port 26 and a stationary exhaust port 27, these ports being of the same size and axially aligned with the corresponding ports in end member 15.

A passage 28 extending through the two end members and the wall of cylinder 23 communicates between the inlet pipe 13 and the stationary inlet port 26, while a second passage 29 extends through the same elements to interconnect the stationary exhaust port 27 with the passage 18 in the end member 15. The inner face 30 of the second end member 25 is smooth and planar, being interrupted only by the stationary inlet port 26 on the central axis and the annular exhaust port 27. The space within the cylinder which is defined by the race and the end members is substantially a right circular cylinder, the planes of the end members being interrupted only by the ports which are sunk therein.

A rotor 31 is placed between the end members inside the race. It is of the same axial length as the race, but of smaller lateral dimensions. The end face 32 of the rotor makes a smooth sealing sliding contact with the inner face 20 of end member 15. End face 33 of the rotor makes a similar sealing sliding contact with the inner face 30 of end member 25. It will be seen that this rotor is able to move freely around the inside of the race in rolling contact therewith, while its end faces remain in constant sliding contact with the end members.

The rotor has at its outer periphery three recesses 34, 35, 36 (see FIG. 3). These recesses are spaced 120' from each other. Each has associated with it a compartment and a number of par-ts, passages, and ports. For clarity in disclosure, only recess 34 will be described and shown in complete detail, it being understood that the other two recesses have identical provisions disposed -120 away from the corresponding elements associated with recess 34. If all of the elements were shown in a single figure, the drawings would be extremely confusing, while a separate drawing of each recess would be repetitious.

The recesses extend from end to end of the rotor, opening onto the race and terminating at the end members. Each has a narrow neck portion '37 adjacent the surface of the rotor and an enlarged stroke portion 38 located radially inwardly of the neck portion. A vane 39, 40, 41 fits respectively in each of the recesses 34, 35 and 36. Each vane has an L-shaped cross-section in a plane perpendicular to the control axis 22. Each vane has a first arm 42 which passes through the neck portion 37 so as to be extendible beyond the periphery of the rotor. The second arm 43 is disposed substantially at a right angle to the first arm and extends transversely across the stroke portion of the recess in contact with both sides thereof so as to form a piston reciprocable within the stroke portion of the recess.

The extensible arms 42 are too short to reach the race wall in all positions of the rotor; that is, the maximum reach of the vane plus the diameter of the rotor, is less than the diameter of the race. The inner portion of the 'recess which is bounded by the second arm 43 and the radially innermost end of the recess comprises an extension chamber '44 of variable volume, the volume being a function of the radial position of the vane. The outer portion of the recess which is bounded by the second arm 43 and the radially outermost end of the stroke portion forms a retraction chamber 45 of variable volume, the volume being a function of the radial position of the vane.

As can be seen best in FIG. 3, the vane is reciprocated in the recess by two classes of force. A first force is exerted by fluid pressure conveyed through an extension chamber supply passage 46 which connects the extension chamber to an extension chamber supply port 47, for supplying pressure to extend the vane. :For convenience, this extension chamber supply port 47 is sunk in the lower end face 33 of the rotor where it slides along the inner face 30 of the second end member 25, and periodically registers with port 26. The chamber supply passage enters the extension chamber 44 at its innermost end.

The second class of force is for the purpose of retracting the vane. To provide pressure for this purpose, a retraction chamber supply port 53 is disposed in the end face 33 of the rotor and is connected by a retraction chamber supply passage 49 to the radially outermost end of retraction chamber 45. The extension chamber supply port 47 and the retraction chamber supply port 53 are spaced from each other and are so disposed at the end of the rotor that as the rotor rolls around the inside of the race, the ports periodically and at separate times register with the stationary inlet port 26 in the end .member 33. The location of the port 26 is shown in dashed line in FIG. 3 for the purpose of illustration, this port being below the section line 3--3 in FIG. 1. The location of port 21 in end member relative to axis 22 is also shown part of this port being behind the rotor in FIG. 3.

Extension chamber supply ports 50, 52 and retraction chamber supply ports 48, 51, respectively, supply wrresponding chambers associated with recesses 35 and 36, through corresponding passageways which are not shown.

As illustrated in FIG. 1, an annular compartment supply groove 54 is sunk in the upper end face 32 of the rotor. This groove is centered-on the central axis 55 of the rotor. It is desirable-to have the compartment supply groove 54 in continuous communication with the port assess? a 211 as shown in FIG. 1, but other dimensions than those shown can give the same continuous communication.

A compartment supply passage extends from the groove 54 to the surface of the rotor adjacent each of the vanes. Compartment supply passage 56 is shown because it is associated with vane 34. Corresponding compartment supply passages (not shown) are provided for compartments adjacent vanes 35 and 36.

Valve means (see FIG. 2) located partly in the compartment supply passage 56 includes an enlargement valve chamber 57 within which a valve plug 58 is operable to open or close the passage by being dropped onto or lifted off of a valve seat 59. The valve seat is partly formed by an insert 60 which is held in place by screws 61. The insert can be removed to permit installation or removal of the plug. This plug has a tendency to beseated on seat .59 because of the air pressure in passage 56 and because of the centrifugal force which results from rotation of the rotor. The valve plug is formed on an arm 62 which arm is pivoted at a joint 63. A cam portion 64 of the arm projects outwardly from the surface of the rotor as the rotor rolls around the race, except when it is pressed inwardly by contact with the race. As can best be seen in FIG. 1, two cam portions 64 are provided, each on an individual arm. The plug is supported on an elongated structure so that it extends a considerable portion of the length of the rotor, as does the valve chamber 57. This large valve area permits a rapid flow of air to an adjacent compartment. In FIG. 3, cam 64 is shown pressed inwardly to open its valve, While the arms of valve members 65 and 66 are shown with their cam portions thrown radially outward (in FIG. 3), so that their valves are closed.

A chamber relief passage 67 intersects the sides of the recess 34 where it is intermittently in communication with extension chamber 44, and always out of communication with retraction chamber 45. The relief passage opens onto the surface of the rotor.

The term compartmen as used herein is defined as the region between the two end members, an extended vane in contact with the race, the race wall, :and the .rotor .where compartment 68 has been enlarged. The compartment opens behind the line of contact between the race and rotor.

FIG. 5 illustrates an end plate used in another embodiment of this invention. This end plate is provided with a circular central pressure port 101, a peripheral extension chamber vent groove 102, and an exhaust groove 103. Grooves 102 and 103 are concentric around pressure port 101. An end plate is aflixed to each end of a race .104 which is the same as race 24 in FIGS. 1-4. Means (not shown, but similar to those in FIG. 11) are provided for supplying fiuid pressure to port 101 making exhaust connection to grooves 102 and 103.

.FIG. 7 shows a rotor .105 which is used in combination with race 104 and a pair of-end plates 100.10 form a vibrator. Rotor 105 has two flat end faces, one of which is shown in FIGS. 7, 8 and 9. If desired, the mirror image of the face shown is provided at theother end thereof. Each of these faces is in sliding contact with one of the end plates 100. Not all of the ports and passages need be provided at each end of the rotor, but instead they may be divided between them in corresponding geometric positions, or they might be provided in only one of them. However, the rotor is better balanced if the reactions at both of its ends are alike.

Rotor 1 05 has vanes 106, 107, 108 in slots 10.9, 2110, 111, respectively. Each of these vanes and slots is provided with a corresponding set of ports and massages. Only the passages associated with vane 106 and slot .109

will be discussed in detail, it being understood that similar provisions are made for each of the other vanes, 120 away from those associated with slot 109. The others are eliminated from the drawings in the interest of clarity.

Three compartment supply ports 112, 113, 114 are provided for slots 109, 111 and 110, respectively. A compartment supply passage 115 interconnects port 112 with the compartment adjacent to and clockwise from vane 106. Similar passages (not shown) are provided for the remaining compartment supply ports and vanes.

Vane extension ports 116, 117 and 118 are provided for slots 109, 111, and 110, respectively. A vane extension passage 119 interconnects port 116 with the inner end of slot 109. Similar passages (not shown) are provided for interconnecting ports 117 and 118 with slots 111 and 110, respectively.

A vane cushioning port 125, 126, 127 is provided for each of slots 109, 111 and 110. Vane cushioning passage 128 interconnects port 125 with slot '109. Passage 128 enters the side of slot 109 at the vane retraction chamber 129, at a point spaced from the outer end thereof. Similar passages (not shown) interconnect ports 126 and 127 with slots 111 and 110.

It will be observed from FIG. 9 that extension chamber vent groove 102 is so disposed and arranged as to overlap the extension chamber '130 of the various vanes in at least some positions of the rotor.

As an alternate to utilizing the extension chamber vent groove 102 to vent chambers 130, or in addition thereto, if desired, extension chamber vent ports 131, 132, 133 may be formed in the end of the rotor at a position such as to periodically overlap exhaust groove 103. Extension chamber vent passage 134 interconnects port 131 with extension chamber 130. Similar passages (not shown) are provided for connecting the other two vanes and ports.

FIGS. 6 and show an alternate means for providing cushioning air pressure to a vane retraction chamber 135. A'cushion bypass 136 (see FIG. 10) is providair under pressure can bypass through groove 136 to the retraction chamber 135 from extension chamber 139, and this bypass air will be cut otf after the vane has thrown just a bit farther out than is shown in FIG. 6. Groove 136 could be used instead of ports 125,

'126 and 127 and their associated conduits, if desired.

The operation of the device of FIGS. l-4 will now be described, it being understood that the direction of movement of the centroid of the rotor is shown by arrow 69, while the direction of rotation of the rotor around its centroid is shown by arrow 70. The centroid moves in a clockwise direction around the race as seen in FIG. 3, while the rotor itself rotates in a counterclockwise direction around its centroid.

The condition of the device as shown in FIG. 3 will be considered as a starting position. The operation of the elements associated with recess 34 will be described in detail, it being understood that the elements associated with recesses 35 and 36 will go through the same movements after the line of contact between the race and the rotor has moved along 120 and 240, respec tively, of the rotors surface. Rotor movement is caused principally by the extension of vane 39, by the enlargement of compartment 68, and by the sequential similar action of corresponding elements associated with the other recesses.

Compartment 68 is about to be opened in FIG. 3.

Extension chamber supply port 47 has just come into registration with stationary inlet port 26 by overlapping the same in its cycloidal path within the race. Air under pressure, is conveyed through passage 46 to extension chamber 44 so as to extend the vane and maintain it in firm contact with the wall of the race. The

force exerted by the vane on the race also tends rotate the rotor.

The cam section 64 of arm 62 has moved into contact with the wall of the race thereby opening the valve means in passage 56 at plug 58. This admits pressure from the compartment supply passage 56 to the compartment 68, which tends to enlarge the compartment, which enlargement is attained by rolling of the. rotor along the race.

It is desirable for pressure to be exerted in the compartments as soon as possible after the line of contact between the rotor and race has swept past a vane. For this reason the cam section 64 is caused to protrude a significant distance beyond the outer periphery of the rotor and also the cam has a projection 71 (see FIG. 2) which tends to cause the cam to contact the race at about the same time that the vane is in tangent contact with the race. Therefore the pressure from passage 57 will be built up at the periphery of the rotor at about the time that the chamber 68 is opened up. The timing of valve means 58 can be adjusted by varying the distance by which the cam protrudes from the rotor, and also by varying the length of projection 71. By not using projection 71, and undercutting the cam at its free end, cam contact can be delayed. This cam is therefore applicable to any desired timing arrangement by changing its length, the distance it projects, and

its angular location on the periphery.

The longer time the cam is in contact with the race, the longer time the air prasure is on in the compartment. The valve means 58 will be held open as long as the cam 62 is in contact with the wall of the race and as can be seen from FIG. 4, this may extend for a considerable number of degrees depending upon the length of arm 62 and the shape of the cam section 64. At any rate when the compartment is opened to the designed volume, the cam moves away from the race by virtue of the continued rotation of the rotor, and the air supply to the compartment is cut off.

Shortly after the condition shown in FIG. 4, vane 39 will no longer be in contact with the race, because it is too short. Then air can leak past the vane 39 from compartment 68, and exhaust quickly into groove 19. In addition, it will be seen that compartment 68 will, itself, overlap groove 19 after a few degrees of rotor movement beyond the position shown in FIG. 4.

At a later time it will be desired to retract the vane,

so that the vane will not project beyond the surface of the rotor when the recess approaches the surface of the race. To facilitate the retraction, the relief passage 67 opens by virtue of extension of the vane and the pressure drops in the extension chamber by exhaust of the air therein into the compartment and out to exhaust. In addition, the chamber supply port 47 will have moved away from the stationary inlet port and no additional air pressure will be supplied to the extension chamber 44.

In FIG. 4 the compartment 68 is about to begin to exhaust. It will be observed that the compartment is about to overlap exhaust groove 19 and 27 in the end members through which the pressure escapes.

When the line of tangency is near a particular vane, the rotor periphery near the vane is moved outwardly beyond the exhaust grooves. The line of contact, a vane, and the end members, then define an expansible compartment for receiving air under pressure. When the rotor rolls far enough that a given compartment is no longer receiving air under pressure, the rotor periphery at this region has moved radially inward beyond the exhaust grooves, and that region is vented. It is also vented past the vanes which are not in contact with the race. It will therefore be appreciated that the major portion of the rotor periphery is, at any given time, vented to exhaust, while there is a part of the periphery, perhaps thereof, which is under pressure as part of an expansible compartment.- The compartments are sequentially pressurized,

vane against the back of the extension chamber.

. chamber.

one after another, around the periphery and this sequential pressurization moves the rotor.

, The position of vane 41 in FIG. 4 illustrates a later condition which is to be occupied by vane 39. This vane is extended to its maximum reach but does not make contact with the race. The outer periphery of the rotor on both sides of this vane is vented through the exhaust grooves, and the extension chamber is vented to the surface of the rotor by virtue of opening of release passage 67 by extension of the vane. As the vane again approaches contact with the wall of the race (for example, see the position of vane 41 in FIG. 3), it is desirable to avoid a sudden blow on a fully extended vane. Sudden blows on extended vanes have caused accelerated vane wear in previous vibrators of this type. In this invention, such a blow is avoided by retracting the vane. For this purpose and with reference to vane 41 in FIG. 3, the retraction chamber supply port 51 will register with the stationary inlet port 26 before such a contact occurs and air admitted to the retraction chamber will retract the vane into the recess. In FIG. 4, vane 40 is shown retracted nearly all the way into the recess by air admitted through port 48. In FIG. 3, port 51 is shown approaching port 26 to accomplish this retraction of vane 41. The relief passage 67 bleeds ofi": sufiicient air from the extension chamber 45 that the vane can be retracted in this manner. When the vane laps over the opening to said relief passage in its retraction stroke, sufficient air is held in the extension chamber and its supply passage to pillow the vane so as to prevent a :hard striking contact of the The vane is therefore substantially retracted so that there is no sudden bending blow on the vane by the race. This markedly lengthens the life of the vanes. Thereafter the vane cycle as described above is repeated.

The operation of the rotor utilizing end plates as shown in FIG. 5, and a rotor as shown in FIG. 7, should be evident from the following, taken in connection with the general description of operation given above for the embodiment of FIGS. 1-4. Only the operation of vane 106 will be discussed. The other vanes operate the same, but 120 and 240 out of phase, respectively, from vane 106. FIG. 8 is earlier in time than FIG. 9. In FIG. 8, vane 106 is being extended by air supplied from pressure port 101 to vane extension port 116, and compartment pressure is being supplied through passage 115. This will cause the rotor to roll in a counter-clockwise direction around its own axis, and clockwise in the race.

Vane cushioning port 125 is about to register with pressure port 101, while compartment supply port 112 is about to leave registration with the pressure port. Registration of port 125 with pressure port 101 will cause a burst of air under pressure to enter in to the vane retraction chamber 129 at the side thereof. Supply of air from passage 128 is cut off by the vane itself when it covers up the opening of passage 128 in to the retraction chamber 129. When the vane closes 0115 passage 128 it traps a quantity of air under pressure in the retraction This trapped air can be made to serve two purposes. First, it acts as a cushion between the vanes arm and shoulder 124 in the rotor that prevents a sharp blow between the two. This markedly decreases vane wear. Second, it provides a store of energy which starts the retraction movement of the vane. The entrance of passage 128 into chamber 129 is far enough spaced from shoulder 124 that an adequate supply of air for this purpose is provided.

While elevated pressure remains in extension chamber 130, the cushioning air will not cause the vane to retract. However, as vane extension port 116 moves out of registration with port 101, port 125 remains in registration, and at that time groove 102 overlaps and vents chamber 130. If provided (or used instead), port 131 registers with groove 103 and also vents chamber 130. Then the cushioning air is effective to move the vane inward, and

as soon-as it moves far enough to open passage 128 again, additional air is supplied to chamber 129 to retract the vane the rest of the way. This is because port remains in registration with port 101 long enough to provide the additional air. All the cushioning air must provide, therefore, is enough energy to move the vane far enough to reopen passage 128 while port 125 still registers with port 101.

Passage 134 enters chamber at the side, andspaced from the inner end thereof, 'so that a cushion of air is trapped at the inner end of the stroke for cushioning purposes. The same effect occurs when only vent groove 102 is used. a Note that in FIG. 9, groove 102 does not overlap the innermost end of chamber 130.

It will now be seen that ports 125, 126 and 127 provide a desirable vane cushioning action, while in combination with either or both of groove 102 and ports 131 -133, a complete system for power-retracting and cushioning the vanes is provided.

In FIG. 9, vane 106 is shown nearly retracted. The vane position at this point is nearly impossible to determine exactly, because of the very rapid rates of motion and reversal thereof. However, it is theorized that vane 106 will coast to very nearly the inner end of slot 109 before the rotor again makes its tangent contact with the race at slot 109. H

At the position illustrated in FIG. 9, no power is supplied to vane 106, nor to its associated compartment. Power will again be supplied thereto just before the posi tion illustrated in FIG. 8, when ports 112 and 116 register with port 101 to supply air to the adjacent compartment and to extension chamber 130, respectively. At that time, groove 103 will vent chamber 129 to allow the vane to beextended. At the position shown in FIG. 8, groove 103 is about to leave registration with chamber 129, so that pressure from port 125, which is about to register with port 101 will be most effective.

The other vanes and ports perform the above-described functions in sequence, 120 and 240 out of phase with vane 106 and its associated ports, so that the operation of the vibrator is continuous, each element functioning periodically in the prescribed order.

It has been found that the above powered action of the vane results in very quick and easy reciprocation of the vane and gives a greater speed of operation of the vibrator for the same power consumption. In addition, the life of the vanes is materially increased because of the substantial elimination of shock of the vane against the rotor at each end of its stroke.

More or fewer than three vanes and recesses could have been supplied if desired but three vanes have been found to be sufficient. Utilizing more vanes simply makes the device more complex and more expensive to manufacture.

To start the device, it is sometimes necessary to shake it so as to bring an extension chamber supply port into registration with a stationary inlet port. Then the rotor is in such a position within the race that it will begin to move, and in a short time it is operating at full speed.

By providing the valve means in the surface of the rotor, the efliciency of this vibrator has been greatly improved and faster speeds have been obtained from the same air flow rates, or, stated conversely, less air has been required for the same speeds. This device operates efl'ectively at about 7800 revolutions per minute on line pressures of about 80 p.s.i.

The life of the vanes 39, 40 and 41 has been greatly increased by providing the retraction ports and passages so that the direct blow between the race and the vane is eliminated. This feature permits the shorter vane to be used etiectively by means of which an existing compartment can bleed past a vane which is out of contact with the wall of the race and utilize a substantially larger portion of the exhaust grooves to discharge compartment air, thereby providing a quicker exhaust cycle which, of course, reduces the back pressure against which the pressure side must work. Expansion past the vane into the next compartment also aids in making a quick pressure drop.

This application is a continuation-in-part of my copending patent application Serial No. 707,197, filed January 6, 1958, entitled Vibrator, now Patent No. 2,891,- 775, June 23, 1959.

This invention is not to be limited by the embodiment shown in the drawings and described in the description, which is given by way of illustration and not of limitation, but only in accordance with the scope of the appended claims.

I claim:

1. In a vibrator of the class which includes a casing having an inner cylindrical curved race with a central axis, end members closing both ends of said casing, the casing being provided with stationary inlet and outlet ports, a free rotor of smaller lateral dimensions than the race positioned inside the race which has a curved peripheral surface interrupted by a plurality of recesses formed therein said rotor having a central aXis and being adapted to roll around inside the race with its curved peripheral surface in rolling contact with the race and with each end of the rotor in flat sliding contact with an end member, there being a vane reciprocably disposed in each of said recesses for making contact with the race in some positions thereof, each vane dividing its respective recess into an extension chamber and a retraction chamber, the retraction chamber being the radially outermost of the said chambers, the improvement comprising: means for conducting cushioning fluid pressure to said retraction chamber near the end of the vanes extension movement to pillow the vane against shock.

2. Apparatus according to claim 1 in which each of the vanes has an L-shaped cross-section viewed in a plane normal to the central axis of the rotor, thereby having a first arm and a second arm, said first arm extending in the direction of reciprocation and making a fluid sealing sliding contact with a portion of said recess, and said second arm extending across the recess so as to divide said recess into said extension chamber and retraction chamber, the retraction chamber being on the 'side of the second arm closer to the peripheral surface,

said means for conducting cushioning pressure comprising a vane cushioning passage entering said retraction chamber adapted to be periodically registered with a :source of pressurized fluid for retracting said vane.

3. Apparatus according to claim 2 in which said cushioning passage enters said vane retraction chamber :at a location spaced from the outer end thereof so that the vane cuts off the cushioning pressure before the vane reaches its outer limit of throw.

4. Apparatus according to claim 2 in which exhaust means are provided to vent said extension chamber when the vane has reached its most-extended position.

In a vibrator of the class which includes a casing having an inner cylindrical curved race with a central axis, end members closing both ends of said casing, the casing being provided with stationary inlet and outlet ports, a free rotor of smaller lateral dimensions than the race positioned inside the race which has a curved peripheral surface interrupted by a plurality of recesses formed therein, said rotor having a central axis and being adapted to roll around inside the race with its curved peripheral surface in rolling contact with the race and with each end of the rotor in flat sliding contact with an end member, there being a vane reciprocably disposed in each of said recesses for making contact with the race in some positions thereof, each vane dividing its respective recess into an extension chamber and a retraction chamber, the retraction chamber being the radially outermost of the said chambers, the improvement comprising: a cushioning port for each vane disposed in an end of said rotor and adapted to periodically register with a stationary inlet port, a cushioning passage interconfr'ecting each cushioning port with a side of a respective retraction chamber at a point spaced from the outer end of said chamber so that the vane closes said passage prior to reaching its outermost position, and exhaust means adapted to vent the respective extension chamber when the vane has reached its outermost position and to continue to vent the same during substantially the remainder of the time the cushioning port remains registered with the inlet port after the vane has reached its outermost position.

6. Apparatus according to claim 5 in which said exhaust means comprises a vent groove in an end member adapted to overlap the extension chamber at the said times.

7. Apparatus according to claim 5 in which said exhaust means comprises a vent port in an end of said rotor for each extension chamber so disposed and arranged as to register with said outlet port at the said times, and a vent passage interconnecting each vent port with the respective extension chamber.

8. Apparatus according to claim 7 in which the vent passages enter the side of the respective extension chambers, at a point spaced from the inner end thereof so that said vent passages are closed by the respective vanes prior to the vanes reaching their innermost position.

References Cited in the file of this patent UNITED STATES PATENTS 2,743,090 Malan Apr. 24, 1956 2,891,775 Malan June 23, 1959 

